1. Field of the Invention
The present invention relates to a display driver, an electro-optical device, and a display driving method.
2. Description of the Related Art
When a voltage is applied to liquid crystals, which is one example of an electro-optical element, the transmissivity of the liquid crystals changes in accordance with transmission characteristics of the liquid crystals. Accordingly, a display driver that drives an electro-optical device including liquid crystals changes the voltage applied to liquid crystals in accordance with the transmission characteristics of the liquid crystals to realize a multi-tone representation.
The applied voltage of the liquid crystals changes depending on production tolerance and a mounting state. The transmission characteristics of the liquid crystals also depend on the liquid crystal material. This means that display drivers are designed so as to be able to regulate the output voltage that depends on production tolerance, the type of liquid crystal material, and the like. In a display driver, an electronic volume control that can variably control the output voltage is used, for example. In this case, according to command settings from a host, such as an MPU (Micro Processor Unit), an electronic volume value that is a parameter for regulating the electronic volume control is changed. The display driver generates an output voltage corresponding to the changed electronic volume value. The electro-optical device is driven by this output voltage.
However, in a conventional display driver, the electronic volume value is incremented according to command settings. A user finds an optimal electronic volume value by carrying out a relative evaluation in which an image displayed by a device is viewed and evaluated every time. This means that it has been necessary for the user to perform command settings numerous times. Accordingly, it is preferable to be able to set the electronic volume value as an absolute value for regulating the electronic volume control of a display driver.
However when the electronic volume value is set using an absolute value, depending on the liquid crystal material being driven and production tolerance, the center value of a range that can be taken by the electronic volume value becomes shifted. This means that even if the electronic volume value is set using an absolute value, it is not possible to correctly regulate the output voltage as intended.
Also, in a conventional display driver, the range that can be taken by the electronic volume value is fixed. By setting a value near an upper limit (or lower limit) of the electronic volume value, an excessive voltage is applied, which can also cause a reduction in the reliability of the electronic volume control and the display driver (and the electro-optical device including this display driver).
The present invention was conceived in view of the above technical problem and it is an object of the present invention to provide a display driver, an electro-optical device, and a display driving method that can regulate an output voltage using an absolute value.
It is a further object of the present invention to provide a display driver, an electro-optical device, and a display driving method that can regulate an output voltage with high precision without reducing reliability.